Skip to main content

What is CMake?

Overview​

CMake is a cross-platform build system generator. It doesn't build your code directly - instead, it generates native build files (Makefiles, Visual Studio projects, Ninja files, etc.) for your platform.

Key Concept

CMake is a meta-build system. You write platform-independent configuration files, and CMake translates them into platform-specific build instructions.

Why Use CMake?​

1. Cross-Platform Compatibility​

Write once, build anywhere:

  • Linux (Unix Makefiles, Ninja)
  • Windows (Visual Studio, MinGW)
  • macOS (Xcode, Unix Makefiles)

2. Modern C++ Support​

  • Automatic dependency management
  • Target-based configuration
  • Package discovery and integration

3. Industry Standard​

Used by major projects:

  • LLVM/Clang
  • Qt
  • OpenCV
  • Boost (partially)

How CMake Works​

The CMake Workflow
  1. Configure: cmake -S . -B build - Generate build files
  2. Build: cmake --build build - Compile your project
  3. Install: cmake --install build - Install binaries

Basic Example​

Here's the simplest possible CMake project:

CMakeLists.txt
cmake_minimum_required(VERSION 3.15)
project(HelloWorld)

add_executable(hello main.cpp)
main.cpp
#include <iostream>

int main() {
    std::cout << "Hello, CMake!" << std::endl;
    return 0;
}

Building:

Terminal
mkdir build
cd build
cmake ..
cmake --build .
./hello

CMake vs Other Build Systems​

FeatureCMakeMakeAutotools
Cross-platform✅ Excellent❌ Unix-only⚠️ Complex
Learning curve⚠️ Moderate✅ Simple❌ Steep
IDE integration✅ Excellent❌ Limited❌ Limited
Modern C++✅ Yes❌ Manual❌ Manual
Remember

CMake files are named CMakeLists.txt (case-sensitive!) and must be in your project root and subdirectories.